Tableware-washing process including a biocide

ABSTRACT

This invention relates to a ware washing process that is conducted in the presence of a biocide. More particularly, but not exclusively, the invention relates to a ware washing process including the steps of (i) washing ware in a washing cavity ( 25 ) of a ware washer ( 10 ) with water and a ware washing detergent; (ii) rinsing the ware in the ware washer with water; and (iii) introducing a biocide into the washing cavity of the ware washer in order to provide a gaseous atmosphere thereof in the washing cavity, the biocide being introduced into the washing cavity prior to or contemporaneously with or subsequently to the washing or rinsing of the ware.

FIELD OF THE INVENTION

This invention relates to a ware washing process. More particularly, butnot exclusively, this invention relates to a ware washing process thatis conducted in the presence of a biocide.

BACKGROUND TO THE INVENTION

In this specification, the use of the word “ware” means items which areused in the preparation and consumption of food and drink, including,but not limited to items such as cutlery, crockery, pots, pans andtableware.

The success of conventional ware washing processes and the associateduse of conventional detergents tends to be found in their removal ofcommon food soils under alkaline conditions, using inorganic alkalis.While these processes remove a large number of fats, proteins andsugars, due to the solubility of such soils in water, it is welldocumented that these soils lend themselves, primarily, to removal underwarm or even hot conditions. Industrial and household auto ware washingis presently, conventionally a warm water multi-stage process, includinga prewash stage (typically conducted at temperatures of 35° C.-40° C.and wherein bulk soils are removed from the ware), a detergent washstage (typically conducted at temperatures of 55° C.-65° C. and whereinthe ware is washed with a detergent) and a rinse stage (typicallyconducted at temperatures of approximately 85° C. and wherein the wareare rinsed so as to remove any residual detergent thereon). The currentpractice requires operation of washing machines at these relatively hightemperatures in order to ensure, first, the breaking of chemical and/orphysical bonds between the soils and the item to be washed and, second,the precipitating out of solution of those soils via a chelation orsequestration process.

A disadvantage of conventional warm water washing is the increasedenergy-consumption associated with generating hot water, as well as theincreased down-time and maintenance of washing machine components,including boilers and elements, that is required, relative to cold-washmachines.

In this specification, the term “warm water washing” means washing attemperatures above 35° C., typically in the range 35° C.-85° C., whilethe analogous term “cold water washing” means washing at temperaturesbelow 35° C., typically in the range 10° C.-25° C.

Another disadvantage associated with warm water washing processes is thefact that they tend to generate relatively hot to humid conditions inthe machine, which conditions are conducive to the sustainability ofvarious forms of bio organisms such as bacteria, algae, fungi andmoulds. These same conditions also create a habitable environment thatis favoured by pests such as cockroaches. Accordingly, warm waterwarewashing processes tend to lend themselves to at least someobjectionable, unhygienic consequences.

The use of biocides, such as ozone, in a warm water washing process isknown in order to overcome the above problems. The ozone is typicallybubbled through water held in the re-circulating or wash tank of a warewashing machine. One of the disadvantages is that an insufficient amountof ozone is infused into the water so as to completely destroy all thebacteria on the ware in the ware washer.

OBJECT OF THE INVENTION

It is an object of the invention to provide an alternative ware washingprocess, that, it is believed, will overcome or at least minimize thedisadvantages and difficulties with the prior art as set out above.

SUMMARY OF THE INVENTION

According to the present invention there is provided a ware washingprocess including the steps of:

-   -   (i) washing ware in a washing cavity of a ware washer with water        and a ware washing detergent;    -   (ii) rinsing the ware in the ware washer with water; and    -   (iii) introducing a biocide into the washing cavity of the ware        washer in order to provide a gaseous atmosphere thereof in the        washing cavity, the biocide being introduced into the washing        cavity prior to or contemporaneously with or subsequently to the        washing or rinsing of the ware.

The water may be at a temperature below 35° C., preferably between 1° C.to 25° C. The biocide may be introduced into the washing cavity ingaseous phase.

In a preferred embodiment of the invention, the biocide is introducedinto the washing cavity of the ware washer independently of the water.Preferably, the biocide is ozone.

In one embodiment of the invention, the ozone is dosed into the washingcavity in the gaseous phase at a rate of 500 to 900 mg/hr, preferably at780 mg/hour.

The ozone is preferably generated by means of an ozone generator havingan ozone outlet in fluid flow communication with the washing cavity.

In one embodiment of the invention, the biocide may be introduced intothe washing cavity at a temperature in the range of 15° C. to 25° C.Furthermore, the biocide may be introduced into the cavity at a pH ofbetween 2 and 12.

In one embodiment of the invention, a pre-rinse stage may be introducedprior to washing the ware, the pre-rinse stage being used to remove bulksoil from the ware using water only. During the step of pre-rinsing, thebiocide may be introduced into the washing cavity at a pH of between 4and 6.

In another embodiment of the invention, water used in the process andexposed to the biocide may be recycled. It will be appreciated thatwhere the biocide is ozone the water exposed thereto may be ozoneinfused water.

The ware washing detergent may include an inorganic alkali, a complexingagent and at least one surfactant.

In a preferred embodiment of the invention, a caustic alkali is used.Preferably the caustic alkali is selected from the class of compoundsselected from the group consisting of alkali metal hydroxides. Morepreferably the inorganic caustic alkali may be sodium hydroxide orpotassium hydroxide.

The complexing agent may be a compound selected from the groupconsisting of a phosphate, an amino carboxylic acid, nitrolo triaceticacid (NTA), ethylenediamine tetra-acetic acid (EDTA), a phosphonic acid,a phosphonobutone, an acrylate and any combination thereof. In apreferred embodiment of the invention, two complexing agents are used,namely EDTA and NTA.

In an embodiment of the invention, the at least one surfactant may beselected from the group consisting of anionic or non-ionic surfactants.

Preferably the ware washing detergent composition comprises a mixture ofsurfactants, preferably a mixture including alkyl polyglucoside (forexample Triton BG-10) and alkylamino polyethoxy prolypropoxy propanol(for example Triton CF-32).

The ware washing detergent may include between 0.1%-55% (m/m) of theinorganic alkali, between 0.1%-45% (m/m) of the complexing agent, andbetween 0.05-20% (m/m) of surfactant.

Additives may also be included in the ware washing detergent, forexample anti scaling agents and/or coupling agents. In one embodiment ofthe invention the anti scaling agent used is Bayhibit™ AM or Belclene®650 which are trade names for products in which the active ingredient is2 phosphono-butane 1,2,4 tricarboxylic acid. The coupling agent ispreferably caustic soda lye.

In a preferred embodiment of the invention, the ware washing detergentcomprises:

% composition Component (by mass) EDTA 4.00 NTA 7.00 Caustic soda lye40.05 Water (softened) 46.70886 Triton BG-10 0.06615 Triton CF-320.08976 Bayhibit ™ AM or Belclene ® 650 0.01963 Water (softened) 2.0656

In a further embodiment of the invention, the step of rinsing the wares,that is step (ii) above, may include the use of a rinse aid compositionwhich may comprise one or more alkoxylated alcohols; and an acid.

The rinse aid composition may include between 0.1% to 90% (m/m) ofalkoxylated alcohol, and between 0.1% to 25% (m/m) of acid.

The chain length of the alkoxylated alcohol may be varied between C₄ toC₂₂.

In one embodiment of the invention the alkoxylated alcohol may comprisean ethoxylated alcohol and the degree of ethoxylation of the ethoxylatedalcohol may be varied between 1 mole to 30 mole ethylene oxide.

In a preferred embodiment of the invention a mixture of alkoxylatedalcohols is used, the mixture comprising alkoxylated alcohols known inthe trade as Synperonic™ LF/RA30 and Synperonic™ LF/RA260.

Preferably, the mixture of the alkoxylated alcohols is 100% active withthe cloud point of a 1% solution of the alkoxylated alcohol in water, ata temperature of less than 22° C.

The acid may be an organic acid and may be selected from the groupconsisting of citric acid, acetic acid, sulfamic acid, phosphoric acidand any combination thereof. Preferably the acid is citric acid.

In a preferred embodiment of the invention, the rinse aid compositioncomprises:

% composition Component (by mass) Propyl alcohol 40.00 Citric Acid 0.10Water (softened) 49.40 Synperonic ™ LF/RA30 5.50 Synperonic ™ LF/RA2605.00

In a preferred embodiment of the invention, the rinse aid compositionmay further include a dye.

According to a second aspect of the invention there is provided the useof a biocide in a ware washing process, the biocide being introducedinto a washing cavity of a ware washer so as to provide a gaseousatmosphere therein.

Preferably the biocide is introduced independently from the water usedto wash ware located in the washing cavity. Preferably the biocide andits introduction into the washing cavity is as described above.

According to a third aspect of the invention, there is provided a warewasher having a washing cavity, the ware washer including introductionmeans for introducing biocide into the washing cavity so as to provide agaseous atmosphere thereof within the washing cavity. In a preferredembodiment of the invention, and where the biocide is ozone, theintroduction means comprises an ozone generator, having an ozone outletin fluid communication with the washing cavity.

The biocide introduction means may be separate from the means forintroducing water into the washing cavity. The washing cavity may beaccessed by means of a door and may be configured to receive waretherein.

It will be appreciated that the ware washer will be in fluid flowcommunication with a source of water and will have a water inlet,wherein water is introduced into the washing cavity, and a water outlet,wherein dirty water is disposed of. In an embodiment of the invention,biocide infused water may be recycled by means of a recycling system.

In one embodiment of the invention, the ware washer also includes meansfor introducing a ware washing detergent and/or a rinse aid compositioninto the washing cavity.

DETAILED DESCRIPTION OF THE INVENTION

Without limiting the scope of the invention and by means of exampleonly, an embodiment of the invention will now be described andexemplified with reference to the accompanying figure.

FIG. 1: is a cross sectional side view of the ware washer used in theware washing process according to the invention.

EXAMPLE 1 Experimental Procedure for the Determination of the Efficacyof Ozone as a Biocide in Ware Washing

Each Formulation was evaluated using a Hobart F25 ware washer.

More particularly, the Hobart F25 ware washer (10) used had beenmodified (not shown) by disconnecting the heating elements so that theware washing process could only be carried out at ambient temperatureswithin the cold water washing range. The particular results discussedbelow were conducted and recorded at an ambient temperature of 17.4° C.

The ware washer (10) was further modified by including an ozonegenerator (15) having an ozone outlet (20) in fluid flow communicationwith a washing cavity (25) of the ware washer (10), so that ozone ingaseous phase could be introduced into the washing cavity (25) therebyto create an atmosphere of ozone therein. The washing cavity (25) can beaccessed by means of a door (30) through which ware (32) may be loadedinto the ware washer (10).

It will be appreciated that the ware washer (10) is connected to asource of water (not shown) and has an inlet (35) for water and anoutlet (40) for soiled water. The ware washer (10) also includes inlets(45) for introducing detergents and/or rinse aids into the washingcavity (25).

The Hobart F25 ware washer was operated on a 6 minute ware washingprocess that included a pre-rinse cycle, a wash cycle and a rinse cycle.The detergent and rinse aid were both dosed automatically into thewashing machine.

The solutions used were made up to the following concentrations:

-   -   detergent: 50 ml in 50 l of water; and    -   rinse aid: 5 ml in 20 l of water.

Uniform standard white dinner plates were used for the experiment. Therate of addition of ozone in gaseous phase was 780 mg/hour giving lessthan 1 ppm concentration and the process of addition of the ozone ingaseous phase into the washing machine during the 6 minute wash cyclewas conducted at a rate of 780 mg per hour.

Bacteria counts were conducted before and after washing, and with andwithout ozone, the results of which are tabulated below in Tables 1, 2and 3. The trial achieved a kill rate of 100% of all bacteria detectedwhen using ozone.

Ozone Usage Trial in Warewashing Machines Scope of Trial

To determine the kill efficacy of ozone on selected bacteria inwarewashing machine.

Bacteria Used

-   -   Staphylococcus aureus;    -   Escherichia coli;    -   Pseudomonas auruginosa;    -   Bacillus subtilis;    -   Salmonella typhi; and    -   Listeria monocytogenes,        the above bacteria having been sourced from the following        batches obtained from the South African Bureau of Standards:    -   S. aureus (STA 53)    -   E. coli (SABS TCC ESC 37)    -   P. aeruginose (PSE 16)    -   B. subtillis (BAC 35)    -   Salmonella (SAL 10)    -   Listeria (LI 5)

Testing Methodology and Tabulated Results

-   1. The surface of the plate used to conduct the testing on was    swabbed prior to testing, and the plate was washed with commercially    available detergent.-   2. The surface of each plate on which testing was to be conducted    was divided into two columns with 12 rows each.-   3. The column on the left hand side was marked “Before Washing” and    the column on the right hand side was marked “After Washing”.-   4. Loopfulls of each bacteria culture were placed and suspended into    5 ml separate aliquots of sterile milk, with each such aliquot being    tested for the presence of antibiotics. Only those aliquots    indicating a negative result for the presence of antibiotics were    used in further experimentation.-   5. Each row on each plate was inoculated with solutions of the    respective bacteria-types specified above.-   6. The plates were left to dry in an incubator for 10-15 minutes.-   7. Each row in the column on the left hand side of the plate marked    “Before Washing” was swabbed so as to establish the presence and/or    quantities of bacteria present on the ware.

TABLE 1 Measured Bacteria Counts Before Washing with Ozone TotalPseudomonas Bacillus Listeria Aerobic Staph E. coli spp CereusSalmonella OXOID Swab Count SGS SGS OXOID 6^(th) SGS spp. 6^(TH) EdDescription SABS 763 1TP:012 1TP:004 EDD (1990) 1TP:011 1TO:018 (1990)Swab 1 0 Swab 2 0 Swab 3 >3000 Swab 4 214 Swab 5 Present Swab 6 PresentSwab 7 Present Swab 8 0

-   8. Plates were then washed in the ware washing machine in the    presence of ozone, together with a ware washing detergent    comprising:

% composition Component (by mass) EDTA 4.00 NTA 7.00 Caustic soda lye40.05 Water (softened) 46.70886 Triton BG-10 0.06615 Triton CF-320.08976 Bayhibit ™ AM or Belclene ® 650 0.01963 Water (softened) 2.0656

-   -   and a rinse aid composition comprising:

% composition Component (by mass) Propyl alcohol 40.00 Citric Acid 0.10Water (softened) 49.40 Synperonic ™ LF/RA30 5.50 Synperonic ™ LF/RA2605.00

-   9. After the wash cycle was completed, the plates was removed from    the ware washer and the right hand side of each row in the “After    Washing” column was swabbed so as to determine whether any bacteria    was present thereon.

TABLE 2 Measured Bacteria Counts After Washing with Ozone TotalPseudomonas Bacillus Listeria Aerobic Staph E. coli spp CereusSalmonella OXOID Swab Count SGS SGS OXOID 6^(th) SGS spp. 6^(TH) EdDescription SABS 763 1TP:012 1TP:004 EDD (1990) 1TP:011 1TO:018 (1990)Swab 9 None Detected Swab 10 None Detected Swab 11 None Detected Swab 12None Detected Swab 13 Absent Swab 14 0

It will be seen from the above table that no bacteria was found on theware and thus a 100% kill rate was achieved when using ozone.

The above testing methodology was repeated without using Ozone. Theresults are shown in Table 3, where it can be seen that without usingozone, not all the bacteria was removed.

TABLE 3 Measured Bacteria Counts Before and After Washing Without Ozone.Pseudomonas Bacillus Listeria Staph E. coli spp Cereus Salmonella OXOIDSGS SGS OXOID 6^(th) SGS spp. 6^(TH) Ed 1TP:012 1TP:004 EDD (1990)1TP:011 1TO:018 (1990) Measured counts 2 × 10⁶ 3 × 10⁶ 19 × 10⁶ 2 × 10⁶4 × 10⁶ 500 Before wash Measured counts 1200 4600 12200 1370 2040 20After wash

Example 2 Description of the Cycles in a Preferred Cold WarewashingProcess

The ware washing process used in the evaluation of the efficacy of ozoneas a biocide in ware washers was a 6 minute cycle which included apre-rinse cycle, wash cycle and rinse cycle. Both the detergent as wellas the rinse aid (as described above) were automatically dosed into theware washer at a rate of 50 ml per 20 l water for the detergent and 25ml per 20 l water for rinse aid. The ozone was dosed into the warewasher in a gaseous phase at a rate of 780 mg per hour. The ozonegenerating unit was designed to commence dispensing ozone into the warewasher on activation of the ware washer, and to cease operation when thewashing cycle had been completed.

Example 3 Relative Performance Evaluation: Variable Rates ofIntroduction of Ozone into the Washing Machine

The experimental procedure as described in Example 1 were repeated,varying only the rate of addition of ozone into the ware washer from 500mg per hour to 900 mg per hour. Consideration and comparison of theresults obtained revealed that the optimum was found at 780 mg per hour.

It is worth noting that the bacterial load used in the experimentaltests conducted were exceedingly high and such loads would not normallybe found in practice and therefore the ozone value could be reducedsignificantly.

The optimum dosages for the detergent and rinse aid were found,similarly, to be 50 ml per 20 l water and 25 ml per 25 l waterrespectively, although this could vary substantially depending on thedegree of soiling and also bacterial load.

It will be appreciated that numerous embodiments of the invention may beperformed without departing from the scope and spirit of the inventionas claimed.

1. A ware washing process including the steps of: (i) washing wares inthe form of items which are used in the preparation and consumption offood and drink in a washing cavity of a ware washer with water and aware washing detergent; (ii) rinsing the ware in the ware washer withwater; and (iii) introducing a biocide into the washing cavity of theware washer in order to provide a gaseous atmosphere thereof in thewashing cavity, the biocide being introduced into the washing cavityprior to or contemporaneously with or subsequently to the washing orrinsing of the ware, and wherein the biocide is introduced in gaseousphase into the washing cavity independently of the water.
 2. The warewashing process of claim 1, wherein the biocide is introduced into thecavity at a cavity temperature of between 15° C. to 25° C.
 3. The warewashing process of claim 1, wherein the biocide is introduced into thewashing cavity at a pH of between 2 and
 12. 4. The ware washing processof claim 1, wherein the biocide is introduced at a pH of between 4 and 6during a pre-rinse step carried out before the washing step of step (i).5. The ware washing process of claim 1, wherein water used in the warewashing process and exposed to the biocide is recycled.
 6. The warewashing process of claim 1, wherein the biocide is ozone.
 7. The warewashing process of claim 6, wherein the ozone is generated by means ofan ozone generator having an ozone outlet in fluid flow communicationwith the washing cavity of the ware washer.
 8. The ware washing processof claim 1, wherein the water is at a temperature of below 35° C.
 9. Theware washing process of claim 1, wherein the ware washing detergentincludes an inorganic alkali, a complexing agent and at least onesurfactant.
 10. The ware washing process of claim 9, wherein the warewashing detergent comprises: % composition Component (by mass) EDTA 4.00NTA 7.00 Caustic soda lye 40.05 Water (softened) 46.70886 Triton BG-100.06615 Triton CF-32 0.08976 Bayhibit ™AM or Belclene ®650 0.01963 Water(softened) 2.0656


11. The ware washing process of claim 1, wherein a rinse aid compositionis used during rinsing, the rinse aid composition comprising at leastone alkoxylated alcohol; and an acid.
 12. The ware washing process ofclaim 11, wherein the rinse aid composition comprises: % compositionComponent (by mass) Propyl alcohol 40.00 Citric Acid 0.10 Water(softened) 49.40 Synperonic ™LF/RA30 5.50 Synperonic ™LF/RA260 5.00


13. Use of a biocide in a ware washing process for washing wares used inthe preparation and consumption of food and drink, the biocide beingintroduced into a washing cavity of a ware washer in gaseous phase,independently of water so as to provide a gaseous atmosphere thereof inthe washing cavity.
 14. The use of claim 13, wherein the biocide isozone.
 15. A ware washer, connectable to a source of water, the warewasher including a washing cavity, wherein ware in the form of itemswhich are used in the preparation and consumption of food and drink maybe loaded therein, a water inlet for introducing water into the washingcavity and at least one inlet for introducing detergent or rinse aidinto the washing cavity, the ware washer being characterised in that itincludes introduction means for introducing biocide into the washingcavity in gaseous phase and independently of water so as to provide agaseous atmosphere thereof in the washing cavity.
 16. The ware washer ofclaim 15, wherein the biocide is ozone and the introduction meansincludes an ozone generator having an ozone outlet in fluid flowcommunication with the washing cavity of the ware washer.